[dm-devel] Re: [PATCH 02/18] io-controller: Common flat fair queuing code in elevaotor layer

[Gui Jianfeng <guijianfeng cn fujitsu com>]

Vivek Goyal wrote:
...
> +/* A request got completed from io_queue. Do the accounting. */
> +void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
> +{
> +	const int sync = rq_is_sync(rq);
> +	struct io_queue *ioq = rq->ioq;
> +	struct elv_fq_data *efqd = &q->elevator->efqd;
> +
> +	if (!elv_iosched_fair_queuing_enabled(q->elevator))
> +		return;
> +
> +	elv_log_ioq(efqd, ioq, "complete");
> +
> +	elv_update_hw_tag(efqd);
> +
> +	WARN_ON(!efqd->rq_in_driver);
> +	WARN_ON(!ioq->dispatched);
> +	efqd->rq_in_driver--;
> +	ioq->dispatched--;
> +
> +	if (sync)
> +		ioq->last_end_request = jiffies;
> +
> +	/*
> +	 * If this is the active queue, check if it needs to be expired,
> +	 * or if we want to idle in case it has no pending requests.
> +	 */
> +
> +	if (elv_active_ioq(q->elevator) == ioq) {
> +		if (elv_ioq_slice_new(ioq)) {
> +			elv_ioq_set_prio_slice(q, ioq);

  Hi Vivek,

  Would you explain a bit why slice_end should be set when first request completes.
  Why not set it just when an ioq gets active?
  
  Thanks.
  Gui Jianfeng